Among many problems impeding the development of a practical rapid and accurate amperometric sensor is a current need for the sensor technology to “break-in” or otherwise rapidly reach chemical, electrical and physical equilibrium with its environment and provide a signal that is an accurately representative of the true analyte level. Attempts to reduce break-in in amperometric sensors have been addressed in a number of ways, for example by using separate and distinct hydrophilic layers in a multi-membrane-based system or by incorporating an aqueous reservoir or environment about the sensor, albeit with limited success, because the break-in improvements to date for these systems have generally only provided limited improvements in break-in. In certain cases, such as an intensive care units (ICUs) setting or for continuous glucose monitoring (CGM) applications, break-in requirements would ideally be a few minutes or seconds. Thus, the current amperometric sensors available on the market may not be capable of achieving the required rapid break-in performance needed for specific applications, such as ICU monitoring of analyte levels in a subject.
In certain medical applications, patients in ICU or other emergency situations may be often fitted with invasive appliances such as catheters so that vital fluids or medicine may be administered intravenously. A physician determining a fluid dosage to be provided to a patient intravenously may need to know symptoms as quickly as possible that may only be determined through blood tests. Just how quickly the information is needed depends on the gravity of the situation. In some cases, the speed with which a physiological parameter may be determined may be the difference between life and death. In those situations, the practice of drawing a blood sample and sending it off for laboratory analysis may be entirely too slow.
A more timely method for measuring blood chemistry to ascertain a physiological parameter of interest may eventually be perfected. Thus, there exists an unmet need to provide intravenous amperometric sensing, in which the concentration of an analyte present in a patient's bloodstream may be determined by locating, within the circulatory system, sensor comprising an enzyme electrode that produces a rapid and accurate electrical current proportional to the true analyte concentration, for example, in less than 30 minutes.